Transparent conductive laminate and process of producing the same

ABSTRACT

A transparent conductive laminate having a completely crystallized, transparent conductive layer on a substrate comprising an organic polymer molding, and a process for producing the same. The transparent conductive layer is excellent in transparency and wet heat confidence and is not excessively low in specific resistivity. The transparent conductive laminate includes a substrate comprising an organic polymer molding having formed thereon a completely crystallized, transparent conductive layer comprising an In.Sn composite oxide having an amount of Sn atom of 1 to 6% by weight based on the total weight of In atom and Sn atom and having a film thickness of 15 to 50 nm, a Hall mobility of 30 to 45 cm 2 /V·S, and a carrier density of from 2×10 20 /cm 3  to 6×10 20 /cm 3 .

This application is a divisional of U.S. patent application Ser. No.10/407,421, filed Apr. 7, 2003 (now U.S. Pat. No. 6,908,666), whichclaims benefit to Japanese Patent Application No. 2002-104676, filedApr. 8, 2002. The above-noted applications are incorporated by referencein their entirety.

FIELD OF THE INVENTION

The present invention relates to a transparent conductive laminatecomprising a substrate comprising an organic polymer molding and atransparent conductive layer comprising an In.Sn composite oxide, formedon the substrate, and a process for producing the same.

DESCRIPTION OF THE RELATED ART

Such kinds of transparent conductive laminates are widely utilized astransparent electrodes for inorganic electroluminescent elements,transparent electrodes for electromagnetic radiation shields,transparent electrodes for analog/digital touch panels, and the like.Especially, in recent years, with the information infrastructure and therapid diffusion of portable communication assistants represented bypersonal digital assistant (PDA), a demand for utilization of touchpanels is rapidly spreading.

Such a touch panel of portable communication assistant is set on aliquid crystal display screen and can be subjected to graphic input byan exclusive pen in place of a keyboard, thereby enabling to displayliquid crystals directly under a transparent input section. A person canrecognize the information of the displayed liquid crystals through thetouch panel as a transparent input element. In recent years, as theimage quality of the liquid crystals of the portable communicationassistant becomes sharp, a transparent electrode layer for touch panelto be set thereon is demanded to have high transparency.

Hitherto, transparent electrode laminates to be used for suchutilization have been prepared by vapor deposition, ion plating,sputtering, or the like. From the standpoint of controllability andreproducibility, the sputtering is most generally employed. Thesputtering is a method in which by using an oxide target identical witha film composition of a transparent conductive layer to be formed on asubstrate, or metal target made of an In—Sn alloy, an inert gas (such asAr gas) is introduced singly or together with a reactive gas (such asoxygen gas) to form a transparent conductive layer made of an In.Sncomposite oxide on the substrate by sputter film formation. However, inthe case where the substrate is made of an organic polymer molding, thefilm cannot be fabricated at high temperature because of poor heatresistance of the substrate, and immediately after the film formation,an amorphous film is partly crystallized in the resulting film. For thisreason, the film product involved problems such that the transparency ofthe film is poor, yellowing of the film is highly observed, and that thechange in resistivity after the wet heat test is large.

In order to overcome these problems, as means for forming a crystallizedfilm on a substrate made of an organic polymer molding, JP-B-3-15536proposes a technology in which a film is fabricated while reducing theamount of oxygen, and the resulting film is post-heated in an oxygenatmosphere in air to convert an amorphous film into a crystallized film.This proposed process gives rise to advantages such that thetransparency of the film is enhanced, the yellowing does not occur, andthat the change in resistivity after the wet heat test is small, so thatthe wet heat confidence is enhanced.

However, according to the above-described process of performing thepost-heating, crystallization is not completed within a short period oftime, but long-term heating at high temperature is required. For thisreason, the productivity is poor, and there is a problem in productquality, such as formation of oligomers in the substrate film. Further,there was a problem that a specific resistivity of the resultingcrystallized film is too low, thereby increasing a consumed electricpower.

SUMMARY OF THE INVENTION

Under these circumstances, an object of the invention is to provide atransparent conductive laminate comprising a substrate comprising anorganic polymer molding having formed thereon a completely crystallized,transparent conductive layer which is free from deteriorations inproductivity and product quality, is excellent in transparency and wetheat confidence, and is not too low in specific resistivity, by sputterfilm formation at a substrate temperature of 150° C. or lower, at whichthe substrate can thoroughly withstand, and then heat treating the filmat low temperature for a short period of time.

The term “completely crystallized” as referred to herein means a statein which crystallized grains are present over the entire surface of thefilm by observation with a transmission electron microscope (TEM).

As a result of extensive and intensive investigations to achieve theabove-described object, it has been found that in sputter film-forming atransparent conductive layer comprising an In.Sn composite oxide on asubstrate comprising an organic polymer molding at a temperature of 80to 150° C., which is a practically allowable heating temperature of thesubstrate, when the transparent conductive layer having a specified filmthickness is formed by sputtering under conditions that the content ofSn in a target is low, an atmosphere where evacuation is performed to aprescribed degree of vacuum, thereby eliminating the moisture andimpurities such as organic gases generated from the substrate, isemployed, and that an oxygen gas in a slight amount such that the plasmaemission intensity of In delicately fluctuates is introduced thereintotogether with an Ar gas, the transparent conductive layer immediatelyafter the film formation is an amorphous film, but when the resultingfilm is heat-treated in air at low temperature of 120 to 150° C. for ashort period of time of 0.5 to 1 hour, the film can be easily convertedinto a completely crystallized film without causing deteriorations inproductivity and material quality.

Moreover, the completely crystallized film by the above specified heattreatment increased in its Hall mobility from 15 to 28 cm²/V·S beforethe heat treatment to 30 to 45 cm²/V·S after the heat treatment, but didnot greatly change in a carrier density, i.e., the carrier densitybefore the heat treatment was 2×10²⁰/cm³ to 5×10²⁰/cm³, and the carrierdensity after the heat treatment was 2×10²⁰/cm³ to 6×10²⁰/cm³. Incontrast, the crystallized film obtained by long-term post-heattreatment at high temperature after the sputter film-formation asproposed by JP-B-3-15536 has a Hall mobility of 18 to 20 cm²/V·S and acarrier density of 5×10²¹/cm³ to 9×10²¹/cm³.

In summary, the completely crystallized film by the above specified heattreatment has peculiar properties such that the Hall mobility is abouttwo times higher and that the carrier density is lower by one order, ascompared with the crystallized film as proposed by the above-citedpatent (JP-B-3-15536). Further, it has also been found that based onthese properties, the completely crystallized film is excellent intransparency and wet heat confidence as a transparent conductive filmand that its reduction in specific resistivity is limited only to abouta half of that before the heat treatment (i.e., immediately after thesputter film formation) so that an excessive reduction of the specificresistivity is prevented as compared with the crystallized film asproposed by the above-cited patent (JP-B-3-15536), in which the specificresistivity is reduced by more than one order after the post-heattreatment, and that an increase in consumed electric power can besuppressed.

The invention has been completed based on these findings.

Accordingly, the invention provides a transparent conductive laminatecomprising a substrate comprising an organic polymer molding, and formedon the substrate a completely crystallized, transparent conductive layercomprising an In.Sn composite oxide having an amount of Sn atom of 1 to6% by weight, preferably 2 to 5% by weight, based on the total weight ofIn atom and Sn atom and having a film thickness of 15 to 50 nm,preferably 20 to 40 nm, a Hall mobility of 30 to 45 cm²/V·S, and acarrier density of 2×10²⁰/cm³ to 6×10²⁰/cm³.

The invention further provides a process for producing the transparentconductive laminate, which comprises:

-   -   (a) a step of sputter film-forming a transparent conductive        layer comprising an In.Sn composite oxide on a substrate        comprising an organic polymer molding, and    -   (b) a step of subsequent post-heating to produce a transparent        conductive laminate having the transparent conductive layer on        the substrate,    -   wherein the step (a) is a step in which a metal target or an        oxide target having an amount of Sn atom of 1 to 6% by weight        based on the total weight of In atom and Sn atom is used,        evacuation is performed to a degree of vacuum of 1.5×10⁻⁴ Pa or        lower at a substrate temperature of 80 to 150° C., and an oxygen        gas is introduced thereinto together with an Ar gas such that        when a plasma emission intensity of In when only the Ar gas is        introduced is defined to be 90, the emission intensity after the        introduction of oxygen gas is 30 to 40 for the metal target and        84 to 90 for the oxide target, respectively, to form an        amorphous transparent conductive layer comprising an In.Sn        composite oxide having an amount of Sn atom of 1 to 6% by weight        based on the total weight of In atom and Sn atom and having a        film thickness of 15 to 50 nm, a Hall mobility of 15 to 28        cm²/V·S, and a carrier density of 2×10²⁰/cm³ to 5×10²⁰/cm³ on        the substrate; and    -   the step (b) is a step in which the amorphous transparent        conductive layer formed in the step (a) is subjected to heat        treatment in air at 120 to 150° C. for 0.5 to 1 hour, to convert        it into a completely crystallized transparent conductive layer        having a Hall mobility of 30 to 45 cm²/V·S and a carrier density        of 2×10²⁰/cm³ to 6×10²⁰/cm³.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE is a microscopic photograph of a transparent conductive layercomprising an ITO film having been subjected to sputter film-formationand heat treatment at low temperature for a short period of time by themethod of Example 1, by observation with a transmission electronmicroscope (magnification: 25,000 times).

DETAILED DESCRIPTION OF THE INVENTION

The substrate used in the invention comprises an organic polymermolding, and organic polymer having excellent transparency and heatresistance are preferably used. Examples of such an organic polymerinclude polyester-based polymers such as polyethylene terephthalate;polyolefin-based polymers; homopolymers such as polycarbonates,polyether sulfones, and polyarylates; copolymers; and epoxy-basedpolymers. Such an organic polymer is molded into a film-like form, asheet-like form, or other forms and then provided for the use. Ifdesired, the molding may be provided with an undercoat or a back-sidecoat.

In the step (a), a transparent conductive layer comprising an In.Sncomposite oxide is formed on the substrate by sputter film formation.This film formation can use not only a standard magnetron sputteringprocess using a DC power source but also various sputtering processessuch as an RF sputtering process, an (RF+DC) sputtering process, a pulsesputtering process, and a dual magnetron sputtering process. In sputterfilm-forming, the substrate temperature must be within the range of from80 to 150° C. in order to not thermally damage the substrate. Byselecting a higher substrate temperature within this specified range,good results for crystallization of the transparent conductive layer tobe formed can be obtained. Usually, the substrate temperature is set atabout 100° C.

The sputter target used in the invention is a metal target (In—Sntarget) or an oxide target (In₂O₃—SnO₂ target), having an amount of Snof 1 to 6% by weight, preferably 2 to 5% by weight, based on the totalweight of In atom and Sn atom. Addition of Sn contributes to enhancementof confidence such as durability of the film. However, so far as thecrystallization is concerned, In₂O₃ is most likely crystallized.Exclusive of the amount of Sn to be incorporated into the In₂O₃ crystallattices, Sn acts as an impurity to suppress the crystallization. Forthis reason, the amount of Sn must be controlled within theabove-specified range.

In conducting the sputter film formation using such a target, the insideof a sputtering device is first evacuated to a degree of vacuum of1.5×10⁻⁴ Pa or less, and preferably 7×10⁻⁵ Pa or less, to prepare anatmosphere from which moisture within the device and organic gasesgenerated from the substrate have been eliminated. The reason for thisis that during the film formation, the presence of the moisture ororganic gases terminates a dangling bond generated during the filmformation to suppress the crystal growth.

Next, an oxygen gas as a reactive gas is introduced together with an Argas as an inert gas into the thus evacuated sputtering device, and thesputter film formation is performed. During this time, it is importantto delicately control the amount of the oxygen gas introduced. Accordingto a general method of introducing a constant amount of the oxygen gasby means of a mass flow controller, since the degree of oxidation of thetarget surface fluctuates every mount, and a hysteresis of oxidation ispresent, it is impossible to perform the film formation of acrystallized film in a stable manner even by the heat treatment afterthe film formation.

The present inventors made extensive and intensive investigations on aPEM (plasma emission monitor) control system utilizing the matter thatthe plasma emission intensity of In as generated during the sputteringdischarge is related to the film formation speed and the film qualityrelying on the degree of oxidation of the sputtering target. As aresult, it has been found that when the plasma emission intensity of Induring the sputter film formation when only the Ar gas is introduced isdefined to be 90, if the oxygen gas is introduced such that the emissionintensity after the introduction of oxygen gas is 30 to 40 for the metaltarget and 84 to 90 for the oxide target, a film that is amorphousduring the sputter film formation can be easily converted into acompletely crystallized film by the subsequent heat treatment in air atlow temperature for a short period of time.

In the method of introducing an oxygen gas such that the In emissionintensity after introduction of the oxygen gas falls within theabove-specified range, a change of the amount of oxygen after theintroduction is so little that it cannot be determined at a certaininstance by a mass flow meter. Incidentally, with respect to theresistivity of the film, it has been confirmed that it exhibits aminimum value when the In emission intensity is 30 for the metal targetand 84 for the oxide target, respectively.

In the invention, by setting the amount of the oxygen gas introducedwithin a slight range, when the film after the sputter film formation onthe substrate is heat treated at low temperature for a short period oftime, it is possible to obtain a transparent conductive laminate havinga completely crystallized transparent conductive layer as describedabove. During the sputter film formation, the film thickness of thetransparent conductive layer should be in the range of from 15 to 50 nm,and particularly preferably from 20 to 40 nm. When the film thickness ofthe transparent conductive layer is less than 15 nm, the crystallizationhardly occurs by the heat treatment at low temperature for a shortperiod of time, whereas when it exceeds 50 nm, the specific resistivityexcessively decreases by the heat treatment, so that the consumedelectric power for the touch panel electrodes is liable to increase.

The transparent conductive layer formed by sputtering on the substrateis an amorphous film comprising an In.Sn composite oxide having anamount of Sn atom of 1 to 6% by weight based on the total weight of Inatom and Sn atom and having a film thickness of 15 to 50 nm, in whichthe Hall mobility is 15 to 28 cm²/V·S, and the carrier density is2×10²⁰/cm³ to 5×10²⁰/cm³.

In the case where the transparent conductive laminate of the inventionis utilized for touch panels, it is subjected to pattern etchingprocessing with an acid. The pattern etching process is carried out at astage immediately after the sputter film formation, namely at a stagebefore the heat treatment. After the heat treatment, the film iscompletely crystallized so that the etching processing is difficult. Onthe other hand, before the heat treatment, the film is an amorphous filmso that the etching processing can be easily carried out.

In the subsequent step (b), the transparent conductive layer after thesputter film formation is subjected to heat treatment in air at lowtemperature for a short period of time. That is, the heat treatment iscarried out at 120 to 150° C. for from 0.5 to 1 hour by properly using adryer, etc. According to this heat treatment, the amorphous film afterthe sputter film formation is converted into a completely crystallizedfilm having a Hall mobility of a larger value of 30 to 45 cm²/V·S and acarrier density of substantially the same value of 2×10²⁰/cm³ to6×10²⁰/cm³. This Hall mobility is about two times higher as comparedwith that of the crystallized film proposed by the above-cited patent(JP-B-3-15536), and this carrier density is lower by approximately oneorder as compared with that of the crystallized film as proposed by theabove-cited patent (JP-B-3-15536).

In general, it is said that donors generated by carrier electrons of atransparent conductive layer comprising an In.Sn composite oxide includean oxygen-deficient portion of an In₂O₃ fluorite crystal lattice and aportion where Sn atom substitutes in the In atom site.

In the invention, since the doping amount of Sn is low, the amount ofthe Sn atom substituted in the In atom site is low. Accordingly, it maybe considered that this matter is a cause to make the carrier densitylow. Further, in the invention, the content of excessive Sn functioningas an impurity and the content of moisture are low. Accordingly, it mayalso be considered that in spite of the heat treatment at lowtemperature for a short period of time, this matter is a cause tolargely grow the crystals, thereby making the Hall density large.

As described above, the transparent conductive layer after the heattreatment has peculiar properties (i.e., novel Hall mobility and carrierdensity) as a transparent conductive layer to be provided on a substratecomprising an organic polymer molding, which have not hitherto beenreported. Especially, it can be said that the transparent conductivelayer after the heat treatment of the invention is a completelycrystallized film where crystals grow very well.

For this reason, the transparent conductive layer after the heattreatment exhibits excellent transparency such that light transmittanceat 550 nm is enhanced by from about 1.5 to 4% as compared with thatbefore the heat treatment. Especially, the enhancement in the lighttransmittance at a wavelength side shorter than 550 nm is remarkable.Further, the transparent conductive layer after the heat treatment doesnot exhibit a yellowing phenomenon and is low in the change ofresistivity in the wet heat test, so that it is excellent in wet heatconfidence. Moreover, in the transparent conductive layer after the heattreatment, the specific resistivity is about a half value of that beforethe heat treatment, and reduction rate of the specific resistivity bythe heat treatment is low. Thus, an increase in the consumed electricpower as touch panel electrodes can be prevented.

Incidentally, in the step (b), when the temperature and time for theheat treatment fall outside the above-specified ranges, theabove-described effects are not obtained. For example, when the heattreatment temperature is lower than 120° C., or the heat treatment timeis shorter than 0.5 hour, the complete crystallization is hardlyachieved. On the other hand, when the heat treatment temperature exceeds150° C., or the heat treatment time exceeds 1 hour, reduction in theproductivity or problems in material quality, such as generation ofoligomers in the substrate film, are liable to occur. Further, atransparent conductive layer exhibiting the above-described filmproperties is hardly obtained. Moreover, inconveniences such anexcessive reduction of specific resistivity likely occur.

The present invention will be described in more detail below withreference to the following Examples, but it should be understood thatthe invention is not construed as being limited thereto.

EXAMPLE 1

An In—Sn metal target (amount of Sn atom: 3% by weight based on thetotal weight of In atom and Sn atom) as a target material and apolyethylene terephthalate (hereinafter referred to as “PET”) filmhaving a thickness of 75 μm as a substrate were installed in a rollingup-type magnetron sputtering device of parallel plate type. The devicewas subjected to dehydration and degassing and evacuated to a degree ofvacuum of 7×10⁻⁵ Pa while rolling up.

In this state, sputter film formation was carried out by a reactivesputtering process with a 3 kW DC by introducing 300 sccm of an Ar gasby heating at a substrate temperature of 100° C. and by setting a plasmaemission intensity of In by only the Ar gas at 90 and then regulating anamount of an oxygen gas introduced while opening and closing anautomatic piezo valve such that the emission intensity after theintroduction of oxygen gas became 33 by PEM, to adjust the film quality.

There was thus formed a 20 nm thick transparent conductive layer made ofa transparent In.Sn composite oxide (hereinafter referred to as “ITO”)on the substrate made of the PET film. The transparent conductive layerwas then subjected to heat treatment by heating at 150° C. for 30minutes to prepare a transparent conductive laminate. With respect tothis laminate, the transparent conductive layer was observed by atransmission electron microscope (TEM) (magnification: 25,000 times). Asa result, it was observed that the completely crystallized ITO film wasformed as shown in the FIGURE.

Further, with respect to this transparent conductive laminate, the Hallmobility and carrier density before the heat treatment (immediatelyafter the sputter film formation) and after the heat treatment weremeasured by the Hall effect measurement. The measurement was carried outusing a “HL5500PC” measurement system manufactured by BIO RAD. Inaddition, the resistivity, the light transmittance at 550 nm, and theresistivity five minutes after immersion in a 5% HCl aqueous solutionwere measured before and after the heat treatment. The results obtainedare shown in Table 1 below.

TABLE 1 Before heat After heat treatment treatment Hall mobility (cm²/V· S) 21.2 37.3 Carrier density (number/cm³) 3.7 × 10²⁰ 4.2 × 10²⁰Resistivity (Ω/square) 400 200 Light transmittance (%) 85 88 Resistivityfive minutes after immersion in ∞ 200 5% HCl aqueous solution (Ω/square)

As is clear from the above results, nevertheless the transparentconductive layer was a thin film having a thickness of 20 nm, whichshould have been originally hardly crystallized, it was wellcrystallized by the heat treatment at low temperature (150° C.) for ashort period of time (30 minutes), so that the light transmittance at550 nm was enhanced by 3% as compared with that before the heattreatment. Further, the reduction in the resistivity after the heattreatment was suppressed to a half of that before the heat treatment, sothat there is no anxiety that the resistivity becomes excessively low bythe heat treatment.

Moreover, before the heat treatment, the resistivity five minutes afterthe immersion in a 5% HCl aqueous solution is indefinite (∞), i.e., thefilm can be easily subjected to etching processing with an acid. On theother hand, after the heat treatment, any change was not found at all inthe resistivity five minutes after the immersion in a 5% HCl aqueoussolution, and hence, it is difficult to undergo the etching processingwith an acid. In other words, the resulting film is stable against theacid.

Still further, separately from the above tests, the transparentconductive laminate after the heat treatment was subjected to wet heattest at 60° C. and at 90% RH for 500 hours. As a result, the change ratein resistivity against the initial resistivity before the test (200Ω/square) was suppressed to 1.1 times. Therefore, the transparentconductive laminate after the heat treatment was also excellent in wetheat confidence.

EXAMPLE 2

An In—Sn oxide target (amount of Sn atom: 4.7% by weight based on thetotal weight of In atom and Sn atom) as a target material and a PET filmhaving a thickness of 75 μm as a substrate were installed in a rollingup-type magnetron sputtering device of parallel plate type. The devicewas subjected to dehydration and degassing and evacuated to a degree ofvacuum of 1×10⁻⁴ Pa while rolling up.

In this state, sputter film formation was carried out in a reactivesputtering process with a 3 kW DC by introducing 300 sccm of an Ar gasby heating at a substrate temperature of 100° C. and by setting a plasmaemission intensity of In by only the Ar gas at 90 and then regulating anamount of an oxygen gas introduced while opening and closing anautomatic piezo valve such that the emission intensity after theintroduction of oxygen gas became 86 by PEM, to adjust the film quality.

There was thus formed a 20 nm-thick transparent conductive layer made ofa transparent ITO film on the substrate made of the PET film. Thetransparent conductive layer was then subjected to heat treatment byheating at 150° C. for 30 minutes to prepare a transparent conductivelaminate. With respect to this laminate, the transparent conductivelayer was observed by a transmission electron microscope. As a result,the completely crystallized ITO film was formed.

Further, with respect to this transparent conductive laminate, the Hallmobility and carrier density before the heat treatment (immediatelyafter the sputter film formation) and after the heat treatment weremeasured in the same manner as described above. In addition, theresistivity, the light transmittance at 550 nm, and the resistivity fiveminutes after immersion in a 5% HCl aqueous solution were measuredbefore and after the heat treatment. As a result, substantially the sameresults as in Example 1 were obtained as shown in Table 2 below.Moreover, separately from the above tests, the transparent conductivelaminate after the heat treatment was subjected to wet heat test in thesame manner as described above. As a result, the transparent conductivelaminate after the heat treatment was excellent in wet heat confidenceas in Example 1.

TABLE 2 Before heat After heat treatment treatment Hall mobility (cm²/V· S) 24.2 37.1 Carrier density (number/cm³) 3.4 × 10²⁰ 4.0 × 10²⁰Resistivity (Ω/square) 380 210 Light transmittance (%) 85 88 Resistivityfive minutes after immersion in ∞ 210 5% HCl aqueous solution (Ω/square)

COMPARATIVE EXAMPLE 1

The sputter film formation was carried out in the same manner as inExample 1, except for changing the target material to an In—Sn metaltarget (amount of Sn atom: 10% by weight based on the total weight of Inatom and Sn atom). There was thus formed a 20 nm thick transparentconductive layer made of an ITO film on a substrate made of a PET film.This transparent conductive layer was then subjected to heat treatmentby heating at 150° C. for 30 minutes to prepare a transparent conductivelaminate.

With respect to this transparent conductive laminate, the Hall mobilityand carrier density before the heat treatment (immediately after thesputter film formation) and after the heat treatment were measured inthe same manner as described above. In addition, the resistivity, thelight transmittance at 550 nm, and the resistivity five minutes afterimmersion in a 5% HCl aqueous solution were measured before and afterthe heat treatment. The results obtained are shown in Table 3 below.

TABLE 3 Before heat After heat treatment treatment Hall mobility (cm²/V· S) 20.1 23.5 Carrier density (number/cm³) 3.8 × 10²⁰ 3.8 × 10²⁰Resistivity (Ω/square) 410 350 Light transmittance (%) 84.5 85Resistivity five minutes after immersion in ∞ ∞ 5% HCl aqueous solution(Ω/square)

As is clear from the above results, an enhancement in the lighttransmittance before and after the heat treatment was not substantiallyfound; and the resistivity five minutes after the immersion in a 5% HClaqueous solution was also indefinite (∞) even after the heat treatment.Hence, although the etching processing with an acid could be performed,the resulting film was poor in stability against an acid in proportionthereto. Incidentally, separately from the above tests, the transparentconductive laminate after the heat treatment was subjected to wet heattest in the same manner as described above. As a result, the change ratein resistivity against the initial resistivity before the test became1.5 times. Therefore, the transparent conductive laminate after the heattreatment was poor in wet heat confidence as compared with that inExample 1.

COMPARATIVE EXAMPLE 2

The sputter film formation was carried out in the same manner as inExample 2, except that the target material was changed to an In—Sn oxidetarget (amount of Sn atom: 9.5% by weight based on the total weight ofIn atom and Sn atom), the evacuation was performed to a degree of vacuumof 8×10⁻⁴ Pa, and that after setting the plasma emission intensity of Inby only the Ar gas at 90, the amount of oxygen gas introduced wasregulated while opening and closing an automatic piezo valve such thatthe emission intensity after the introduction of oxygen gas became 80.There was thus formed a 20 nm thick transparent conductive layer made ofan ITO film on a substrate made of a PET film. This transparentconductive layer was then subjected to heat treatment by heating at 150°C. for 30 minutes to prepare a transparent conductive laminate.

With respect to this transparent conductive laminate, the Hall mobilityand carrier density before the heat treatment (immediately after thesputter film formation) and after the heat treatment were measured inthe same manner as described above. In addition, the resistivity, thelight transmittance at 550 nm, and the resistivity five minutes afterimmersion in a 5% HCl aqueous solution were measured before and afterthe heat treatment. The results obtained are shown in Table 4 below.

TABLE 4 Before heat After heat treatment treatment Hall mobility (cm²/V· S) 27 28 Carrier density (number/cm³) 3.3 × 10²⁰ 2.5 × 10²⁰Resistivity (Ω/square) 350 450 Light transmittance (%) 85 85.5Resistivity five minutes after immersion in ∞ ∞ 5% HCl aqueous solution(Ω/square)

As is clear from the above results, an enhancement in the lighttransmittance before and after the heat treatment was not substantiallyfound; and the resistivity five minutes after the immersion in a 5% HClaqueous solution was also indefinite (∞) even after the heat treatment.Hence, although the etching processing with an acid could be performed,the resulting film was poor in stability against an acid in proportionthereto. Incidentally, separately from the above tests, the transparentconductive laminate after the heat treatment was subjected to wet heattest in the same manner as described above. As a result, the change ratein resistivity against the initial resistivity before the test became2.0 times. Therefore, the transparent conductive laminate after the heattreatment was poor in wet heat confidence as compared with that inExample 2.

In the light of the above, according to the invention, in sputter filmformation of a transparent conductive layer comprising an In—Sncomposite oxide on a substrate comprising an organic polymer molding ata temperature of 80 to 150° C., which is a practically allowable heatingtemperature of the substrate, when the transparent conductive layerhaving a film thickness of from 15 to 50 nm is formed by sputteringunder conditions that the content of Sn in a target is low, anatmosphere where evacuation is performed to a prescribed degree ofvacuum, thereby eliminating the moisture and impurities such as organicgases generated from the substrate, is employed, and that an oxygen gasin a slight amount such that the plasma emission intensity of Indelicately fluctuates is introduced thereinto together with an Ar gas,and the resulting film is heat treated at low temperature of 120 to 150°C. for a short period of time 0.5 to 1 hour, a transparent conductivelaminate having a completely crystallized, transparent conductive layer,which does not cause deteriorations in productivity and materialquality, is excellent in transparency and wet heat confidence, and isnot excessively low in specific resistivity, can be obtained.

It should further be apparent to those skilled in the art that variouschanges in form and detail of the invention as shown and described abovemay be made. It is intended that such changes be included within thespirit and scope of the claims appended hereto.

This application is based on Japanese Patent Application No. 2002-104676filed Apr. 8, 2002, the disclosure of which is incorporated herein byreference in its entirety.

What is claimed is:
 1. A process for producing a transparent conductivelaminate comprising a substrate which comprises an organic polymermolding, and formed thereon a completely crystallized, transparentconductive layer comprising an In—Sn composite oxide having an amount ofSn atom of 1 to 6% by weight based on the total weight of In atom and Snatom and having a film thickness of 15 to 50 nm, a Hall mobility of 30to 45 cm²/V·S, and a carrier density of 2×10²⁰/cm³ to 6×10²⁰/cm³, saidprocess comprising: (a) a step of sputter film formation of atransparent conductive layer comprising an In—Sn composite oxide on asubstrate comprising an organic polymer molding including a step ofcontrolling a variation of oxygen gas in response to fluctuations ofdegrees of oxidation of a target during sputter film formation by usinga plasma emission control system, wherein the step (a) is a step inwhich the target having an amount of Sn atom of 1 to 6% by weight basedon the total weight of In atom and Sn atom is used, evacuation isperformed to a degree of vacuum of 1.5×10⁻⁴ Pa or lower at a substratetemperature of 80 to 150° C., and a mixed gas of an oxygen gas and an Argas is introduced thereinto such, in a step of controlling the variationof oxygen gas; when a plasma emission intensity of In when only the Argas is introduced is defined to be 90, the plasma emission intensityafter the introduction of oxygen gas is 30 to 40 for when the target isa metal target and from 84 to 90 for when the target is an oxide target,respectively, to form an amorphous transparent conductive layercomprising an In—Sn composite oxide having an amount of Sn atom of 1 to6% by weight based on the total weight of In atom and Sn atom and havinga film thickness of 15 to 50 nm, a Hall mobility of 15 to 28 cm²V·S, anda carrier density of 2×10²⁰/cm³ to 5×10²⁰/cm³on the substrate; and (b) astep of subsequent post-heating after sputter film formation to producethe transparent conductive laminate, wherein the step (b) is a step inwhich the amorphous transparent conductive layer formed in the step (a)is subjected to heat treatment in air at 120 to 150° C. for 0.5 to 1hour, to convert the amorphous transparent conductive layer into acompletely crystallized transparent conductive layer having a Hallmobility of 30 to 45 cm²V·S and a carrier density of 2×10²⁰/cm³ to6×10²⁰/cm³.
 2. The process as claimed in claim 1, wherein the amount ofSn atom in the target is 2 to 5% by weight.
 3. The process as claimed inclaim 1, wherein said substrate temperature is about 100° C.
 4. Theprocess as claimed in claim 1, wherein said film thickness is 20 to 40nm.